Air-admittance device and method for making same

ABSTRACT

There are provided methods for fabricating devices for admitting air to a closed container while preventing passage of a water-based fluid therethrough. These devices comprise a plurality of hydrophobic capillaries or a hydrophobic reticulated microporous material. The devices comprising hydrophobic capillaries are fabricated by a variety of techniques, such as those employing extrusion, pultrusion, fugitive mandrel removal or a combination of these techniques. The devices comprising hydrophobic reticulated microporous material are fabricated by techniques such as foaming, sintering, template replication, incorporation of sacrificial particles or a combination of these techniques.

CROSS REFERENCE TO RELATED APPLICATION

This application is a Continuation-In-Part of application Ser. No.10/144,571, filed May 13, 2002 now U.S. Pat. No. 6,818,162.

RIGHTS OF THE GOVERNMENT

The invention described herein may be manufactured and used by or forthe Government of the United States for all governmental purposeswithout the payment of any royalty.

BACKGROUND OF THE INVENTION

The present invention is directed to baby-feeding nipples, and, inparticular, relates to baby-feeding nipples based on capillary action.

At present there is no baby bottle nipple on the market that evenclosely approximates the attributes of the human breast nipple, whichdelivers a continuous supply of milk without entrained air and withouthard sucking until the reservoir is empty. In addition, as the babybites on the human nipple, although it hurts the mother, the fluid flowis not completely cut off.

Commercial baby bottle nipples are made in the form of a hollow rubbershell with a feeding-tip extending from a bulbous portion, which iscarried on a flexible and pliable outwardly extending flange. The typesof nipples on the market differ principally in the number, size, andtypes of holes or slits in the feeding-tip and in the external shapethat fits into the infant's mouth. In contrast to the human nipple,there are several inherent problems associated with this design. As thebaby sucks on the nipple and drains the bottle, the pressure inside thebottle is gradually reduced, resulting in a vacuum. As the babycontinues to suck, the pressure will ultimately be reduced to such anextent that the nipple collapses and liquid can no longer be sucked outby the infant. At this point the infant becomes frustrated and sucksharder, frequently swallowing air, which is very undesirable since itresults in colic and/or the need for burping. In addition, if the babybites on the hollow nipple, or if particulates clog the nipple holes,the flow is totally cut off and no fluid is delivered. This alsofrustrates the infant. Finally, dentists have found that current nippletechnology damages a baby's bite; they recommend that babies breast feedrather than use current nipple technology.

It is obvious that there is a need to improve on the currentstate-of-the-art in baby feeding technology. There have been numerousattempts in the past to improve upon baby-feeding technology, inparticular, nipple design. In fact, in the patent literature there arescores of patents in this area, some of which go back more than acentury. To address the problem of a vacuum forming in the bottle, therehave been numerous means to allow the entrance of air. One of the oldestexamples, from 1901, involved the use of a concentric nipple design.Other examples involve the use of a tube or check valve in the nipplemounting flange or an air valve on the side of the bottle to let airinto the bottle. An alternate approach to compensate for the vacuum isto use a collapsible plastic sac inside a baby bottle shell. Inoperation, the sac collapses during feeding, thus minimizing the amountof air that the baby ingests. A recent example (U.S. Pat. No. 6,053,342)involves the use of a flexible diaphragm with slits for pressureequalization.

Even with these improvements, the baby can still close off the nipple bybiting, can still swallow air, and, in contrast to the human breast, thebaby must suck harder to get the fluid. To alleviate this last problemand deliver fluid to the infant without hard sucking, several differentversions of a nipple pump with a check valve have been proposed, forexample, U.S. Pat. No. 2,960,088. These pumps are actuated by the infantbiting on the nipple. Each time the infant presses down on the nipple,fluid is squirted into its mouth and each time the infant releases thenipple, the nipple is refilled.

For more than a century there have been scores of improvement patentsfor a baby bottle system that delivers fluid to an infant. Some of thesehave involved the fluid container, others have involved the nipple, andstill others have involved both. To the applicants' knowledge the onlytwo significant improvements over the past century that are incommercial production are the collapsible sack and the elastomericdiaphragm with resealable perforations both of which help to eliminatethe sucking of air by the infant. Most other approaches tend to becomplex in construction, difficult and expensive to manufacture,difficult to clean and sterilize, or simply do not function asdescribed.

Although two separate systems for dealing with the vacuum generatedinside of the bottle are commercially available, it should be noted thatthere are still shortcomings associated with these two approaches. Thethin plastic bag that collapses during feeding minimizes but does noteliminate ingestion of air and must be replaced after each feeding,because it cannot be sterilized. This, of course, results in acontinuing expense beyond that of the initial expense of the bottle andnipple.

The elastomeric diaphragm with resealable perforations, being amechanical type of check-valve, also possesses the shortcomingsassociated with this type of system. Like all check-valves, it issusceptible to leakage due to incomplete closure. This can result fromclogging, such as particulates lodging in the slit, or from distortionsin the slits. These distortions can be caused by elastomeric materialchanges (resulting from prolonged exposure to heat or sunlight forexample) or from mechanical stresses on the edges of the slits as theyopen or close. In addition, like all check-valves, there is a thresholdvalue at which each of the valves open. This threshold value, because ithas to keep the valve from leaking, has to be significant and can exceedthe sucking effort of a weak infant, especially after changes resultingfrom either time or usage. Of course, the valve will not function atthis point. Additionally, if, for example, a sugar-based fluid is placedin the bottle and then allowed to dry on the diaphragm, the slit valveswill not open at all until the sticky substance is removed. Finally, itshould be noted that it is very difficult to clean residual fluid andbacteria from the slits when they are in their normally closed position.This can result in illness.

Clearly there is a need for a simple, inexpensive baby bottle nipplethat more closely resembles the human breast nipple and its positiveattributes.

Accordingly, it is an object of the present invention to provide aprocess for making a nursing nipple that delivers milk or water-basedfluid to an infant without hard sucking by means of capillary pressurein the same way as the human breast.

Another object of the present invention is to provide a process formaking a nipple with microscopic fluid pathways that cannot beclosed-off when an infant bites on them and are easy to completely cleanand sterilize.

Yet another object of the present invention is to provide a process formaking a nipple having leak-proof hydrophobic microscopic pathways thatare always open to relieve the slightest vacuum.

A further object of the present invention is to provide a process formaking a nipple having an integral microscopic filter in the nipple thatwill keep particulates from clogging the nipple.

Other objects and advantages of the invention will be set forth in partin the description which follows, and in part will be obvious from thedescription, or may be learned by practice of the invention. The objectsand advantages of the invention may be realized and attained by means ofthe instrumentalities and combinations particularly pointed out in theappended claims.

SUMMARY OF THE INVENTION

In accordance with the present invention there are provided methods forfabricating baby bottle nipples which mimic the function of the humanbreast nipple. In the human breast nipple, milk is delivered to the babythrough 15-25 fluid-delivery capillaries called lactiferous ducts. Theseducts are 2-4 centimeters in length and 500-900 microns in diameter.Baby bottle nipples fabricated in accordance with the methods of thisinvention have the common feature of at least one hydrophilic fluiddelivery passage. In one embodiment, the fluid delivery passage is amicrotube, as hereinafter described. In another embodiment, the fluiddelivery passage is a microchannel, also hereinafter described. In yetanother embodiment, the fluid delivery passage comprises a porousreticulated foam with interconnected pores. In each of theseembodiments, the fluid delivery passage has at least one dimension inthe range of 1-2000 microns. Also provided are processes for fabricatingfilters for separating solids from liquids.

All the nipples described in this application function on the basis ofcapillary pressure and thus the interior walls of the fluid-deliverypassages in all the nipples in this application are made of, convertedto, or coated with, a hydrophilic material that milk, water, juice, orother water-based liquids will wet. If the interior surface of thefluid-delivery passage is wet by the water-based fluid, then when thereis a water-based fluid reservoir in contact with the bottle side of thenipple, the water-based fluid will be sucked into the fluid-deliverypassages. That is, if the contact angle between the liquid and thecapillary surface of the passage is 90° or less, there will be noresistance to the flow of the liquid. In addition, the smaller thecontact angle or the smaller the capillary passage, the greater will bethe capillary force drawing the liquid into the capillary. There are twoadditional positive ramifications resulting from using a capillary witha hydrophilic wall for fluid-delivery. In contrast to prior art, notonly will this type of capillary be extremely easy to clean andsterilize, but in addition, if the infant partially closes off thepathway by biting on the nipple, the capillary pressure will increase,providing fluid at increased pressure through the smaller opening in thefeeding tip. Thus, like the human nipple, this invention provides milkat the baby's end of the nipple without hard sucking. This means that,using the present technology, the shape of the nipple can be much closerto that of an actual human breast. In addition, these fluid-deliverypassages embedded in a solid or non-reticulated porous flexible nipplebody (like the human nipple) will not be easily closed off if the babybites on the nipple. This solid or non-reticulated porous flexiblenipple will therefore not adversely affect the baby's bite as is commonwith hollow nipples.

In addition to the features already mentioned, the nipples described inthe present application provide a means for letting air into the bottlein a continuous fashion without a pressure threshold, therebyeliminating the vacuum generated by the sucking infant. This isaccomplished by placing microscopic hydrophobic passages in the form ofair-admittance channels or pores in an area of the nipple which is neverin the infant's mouth. The walls of these air-admittance capillaries orpores are made of, converted to, or coated with a hydrophobic materialso that air can enter the bottle, but the water-based fluid cannot flowout of the bottle if the minimum cross-sectional dimension is smallenough. In the present invention, the cross-sectional dimension isusually less than 300 microns. With these small capillaries an adequaterate of air-admittance is achieved by using a plurality ofair-admittance capillaries.

Finally, some of the nipples described in the present applicationincorporate an integral microscopic filter to keep the capillaries orpassages that deliver water-based fluid to the infant from clogging. Thewalls of the pores or channels in this microscopic filter are fabricatedfrom or coated with a hydrophilic material. The minimum cross-sectionaldimension of the pores or capillaries in the filter must be smaller thatthose that deliver milk or other water-based fluid to the infant so thatthey can effectively keep particulates that would clog thefluid-delivery pores or capillaries from entering the nipple.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is a cross-section through the center of a prior art nipple;

FIG. 2 is a cross-section through the center of a nipple having aplurality of fluid-delivery passages;

FIG. 3 is a cross-section through the center of a baby nipple withtapered fluid-delivery passages;

FIG. 4 is a cross-section through the center of a baby nipple with aseparately fabricated core comprising a plurality of fluid-deliverypassages;

FIG. 5 is an end view, from the attachment end, of the nipple of FIG. 4;

FIG. 6 illustrates the separately fabricated core of the nipple of FIG.4;

FIG. 7 is a cross-section through the center of a baby nipple having ahollow center portion;

FIG. 8 illustrates a trilobal capillary shape;

FIG. 9 illustrates a rectangular capillary shape;

FIG. 10 illustrates film lay-up for fabrication of rectangularcapillaries;

FIG. 11 illustrates a rectangular capillary core member prior to removalof sacrificial materiel;

FIG. 12 is an end view, from the attachment end, of a nipple havingrectangular capillaries;

FIG. 13 illustrates an alternate lay-up for fabrication of rectangularcapillaries;

FIG. 14 illustrates a film-like member having projections on both sidesfor use in the lay-up shown in FIG. 13;

FIG. 15 illustrates another alternate lay-up for fabrication ofrectangular capillaries;

FIG. 16 illustrates an extruded nipple core with circularly configuredcapillaries;

FIG. 17 is a cross-section through the center of a nipple having areticulated porous core;

FIG. 18 is a cross-section through the center of a nipple having aplurality of fluid-delivery passages and an integral filter; which areattached to a bottle having a vent plug for air-admittance in the bottomof the bottle.

FIG. 19 is a cross-section through the center of a nipple having areticulated porous core and a separate filter; which are attached to abottle having a vent plug for air-admittance in the side of the bottle.

FIG. 20 is a cross-section through the center of a nipple having aplurality of fluid-delivery passages and air-admittance capillaries;

FIG. 21 is a cross-section through the center of a baby nipple with aseparately fabricated core comprising a plurality of fluid-deliverypassages;

FIG. 22 is a cross-section through the center of a baby nipple with aseparately fabricated core comprising a plurality of fluid-deliverypassages;

FIG. 23 is a cross-section illustrating a plurality of pultruded coatedfibers;

FIG. 24 is a cross-section illustrating a filter assembly comprising aplurality of the assemblies shown in FIG. 23;

FIG. 25 is a cross-section of a nipple core formed by stacking andinterlocking three pieces of material; and

FIG. 26 is a cross-section through the center of a baby nipple with aseparately fabricated core comprising a plurality of fluid-deliverypassages and with a separately fabricated air-admittance membrane.

DETAILED DESCRIPTION OF THE INVENTION

Referring to the drawings, and in particular to FIG. 1, there is shown aprior art nipple, generally represented by reference numeral 10. Nipple10 is designed for use in combination with a baby bottle, not shown. Thebaby bottle can be a plastic or glass (hard) bottle for dispensingliquids therefrom. Nipple 10 has a tip 12 at its top end, shown asrounded, but can be flat or have any shape as is known in the art. Tip12 has an aperture 14 passing through its center to provide a conduitfor the liquid to be dispensed from the bottle. Aperture 14 can beformed in any fashion and of any shape known in the art, such as a slitor slits. Below the rounded tip 12, the nipple 10 flares outward to forma torso 16. Torso 16 preferably has an annular indent 18, adjacent itslower end. Below torso 16, nipple 10 terminates in a radial orhorizontal flange 20. Flange 20 assists in mounting nipple 10 in aretaining ring, not shown, and sealing the free edge of a bottle whenthe nipple is mounted onto the bottle. Annular indent 18 facilitatesalignment and securing of nipple 10 in a retaining ring.

Referring to FIG. 2, there is shown a nipple according to the presentinvention, generally represented by the reference numeral 22. Nipple 22is designed for use in combination with a baby bottle, not shown. Thebaby bottle can be a plastic or glass (hard) bottle for dispensingliquids therefrom. Nipple 22 has a rounded tip 24 at its top end. Tip24, which is shown as rounded, but can be flat or have any shape. Belowthe rounded tip 24, the nipple 22 flares outward to form a torso 26.Torso 26 preferably has an annular indent 28, adjacent its lower end.Below torso 26, nipple 22 terminates in a radial or horizontal flange30. Flange 30 assists in mounting nipple 22 in a retaining ring, andsealing the free edge of a bottle when the nipple is mounted onto thebottle. Annular indent 28 facilitates alignment and securing of nipple22 in a retaining ring.

The body of nipple 22 is solid and has at least one fluid-deliverypassage 32 extending from the termination of tip 24 toward the flangeend of nipple body 22 that makes contact with the fluid in theaforementioned bottle. Each fluid-delivery passage 32 has a hydrophilicinterior surface, at least one cross-sectional dimension in the range of1-2000 microns and is aligned in such an orientation as to deliverwater-based fluid from the bottle or other container to a sucking infanton the other end by capillary action.

In this embodiment, the baby bottle nipple employs microtubes as fluiddelivery passages. Microtube technology is disclosed in U.S. Pat. Nos.5,011,566 and 5,352,512. Briefly, this technology comprises placing acoating on a sacrificial fiber or fibers and then removing the fibers.If the space between the coated fibers is not filled in, tubes willresult. However, if the space between the coated fibers has been filledin, capillaries will be produced when the fibers are removed. The innerdimensions and contours of these capillaries will perfectly match thedimensions and contours of the fiber surfaces from which they wereformed if the material is rigid.

Before continuing with the detailed description of the presentinvention, it is prudent to define some terminology. This isnecessitated by the fact that microtube and thin-film layeringtechnology offers the capability to make microscopic passages that haveheretofore been impossible to fabricate.

Historically, names for thread-like filaments and tubes with smalldiameters and high-aspect ratio have been material- and sometimesapplication-sensitive. For example, if a filament is spun from cotton,glass, or a polymer, it is called a “fiber”, while if its composition ismetallic it is termed a “wire”. In a similar way, a small tube drawndown from a larger glass tube is usually called a “capillary”, while apolymer filament extruded in tubular form is called a “hollow fiber”. Asmall tube made from human tissue it is called a “duct”, while a smalldiameter metallic tube used to extract fluid from the body is called a“cannula”.

The term “capillary” has traditionally referred to a small round tubebecause historically it has only been possible to form microscopic roundtubes. The reasons for this lie in manufacturing technology. That is,capillaries are usually drawn from glass tubing and the effect ofsurface tension on the soft glass wall of the tubing being drawnprecludes the fabrication of non-rounded features.

With the advent of microtube and thin-film layering technology thesetraditional historical terms have become blurred. The term “fiber” isused in this application in its broadest sense and refers to natural orsynthetic filaments of any material, such as polymer, cellulose, glass,ceramic, or metal. The term “microtube”, in turn, encompassesmicroscopic tubes that are formed by coating fiber substrates and thenremoving the fiber substrate leaving a microscopic tube. The term“capillary” is used in this application to describe microscopic channelsof any cross-sectional and axial shape made from any type of materialand imbedded in a solid structure. This term was chosen because thenipples described in this invention function on the basis of capillaryattraction. Some of the capillaries in this application are fabricatedby means of microtube technology while others are not. These microtubescan have non-circular shapes, due to the fact that the fugitive fibersfrom which the microtubes are fabricated can have non-circular shapesbecause they are not hollow. When non-circular fibers are coated and thefibers are thereafter removed, a non-circular tube, channel, orcapillary is produced.

A first step of manufacture is to select a material for the nipple body.Such materials are widely known in the art, including silicone rubber,latex and other elastomeric materials. Ideally, the material used shouldsimulate the mother's natural nipple in texture, surface quality,resiliency, and rigidity. In fact, different types of latex (or othermaterial) having different characteristics may be used in the samearticle.

Another first step of manufacture using microtube technology is toselect a suitable fugitive fiber or fibers. The fiber can be of anycomposition, such as metal, polymer, glass, or carbon. A polymer ispreferred for many applications since it possesses controlled elasticityand is easy to remove by methods such as solvation, depolymerization,reaction, phase change and the like. The fiber can have almost any axialor cross-sectional shape and can have any dimensions needed for theapplication as long as at least one cross-sectional dimension is in therange of 1-2000 microns. Depending on the size of the capillary formed,it is possible that only one capillary will be needed for delivery ofwater-based fluid through the nipple.

Fibers with different compositions, cross-sectional and/or axial shapesand dimensions can be used to form a single nipple. The main requirementfor the sacrificial or fugitive fiber is that it be chosen so that theprocedure used to remove the fiber does not adversely affect anymaterial used in the nipple. It is usually preferable to use a porous orhollow fiber where possible in order to aid removal of the fiber. Forthe baby nipple, the preferred polymer fiber is made of polyvinylalcohol because such fiber can be removed by dissolving in water at anelevated temperature. This removal process is non-toxic, thus leavingbehind no toxic solvent and, as a benefit, would pre-sterilize thenipple for use. Other sacrificial materials include treated soy proteinand corn zein.

Nipple 22 is fabricated by placing at least one sacrificial or fugitivefiber in a suitable mold, fixture, extrusion or pultrusion device, withan orientation principally along the axis of the nipple and, if aplurality of fluid-delivery passages are desired, with a desired spacingbetween pieces of fugitive material. This spacing can be maintainedmechanically or by pre-coating the fugitive fiber with the nipple bodymaterial, or other suitable material. Sufficient nipple body material isthen provided to fill the interstices between the pieces of fugitivematerial and to form the external dimensions of the nipple body. Aftersolidifying the nipple body material, by appropriate technique, thenipple is removed from the mold, fixture, extrusion, or pultrusiondevice, and, if necessary, nipple body material is removed to bring thenipple to final external dimensions. Sufficient solidified nipple bodymaterial is removed from the tip end and from the flange end to exposethe end(s) of the fugitive fiber(s). The fugitive fiber(s) is(are)removed as described previously, thereby leaving fluid-delivery passageswith interior dimensions equal to or less than the external dimensionsof the fugitive material.

The sacrificial fibers can also be aligned and held in position by othermeans, such as by wrapping around a large mandrel, flocking, fixturing,centrifugal force, electrostatic force, or magnetic force. For example,fibers that can be magnetized, such as some metals and ceramics, can bealigned parallel to each other in a magnetic field because of the ratioof their length to cross-sectional dimensions. Non-conducting fibers canbe aligned similarly in an electrostatic field. Any type of fibers withsignificant length to cross-sectional dimension ratio can easily bealigned along the radius of a centrifuge provided one end isimmobilized. Regardless of the technique used to align the fibersparallel to each other, the spacing between adjacent fibers can becontrolled by coating the fibers before alignment. If the coating on allthe fibers is uniform, the thickness of this layer of material on eachfiber is usually equal to half the desired separation distance of thecapillaries. However, there is no requirement for all the fibers to havea coating with the same thickness. The coating on the fibers is at leastpartially solidified while the fibers are held in alignment to group aplurality of coated fibers together.

Although the fluid-delivery passages in the nipple need to behydrophilic, it should be noted that the material used to make thenipple body need not be hydrophilic. If the material used to make thenipple body 22 is hydrophilic no additional manufacturing steps areneeded because a water-based fluid will be delivered from the containerend of nipple 22 to the feeding-tip 24 by capillary action. However, ifthis nipple body material is hydrophobic and is, therefore, not wet bymilk or a water-based fluid, the capillary walls of the nipple can betreated, for example, chemically or with radiation to graft hydrophilicgroups onto the nipple body material forming the inner capillary wallsin order to make them either hydrophilic, or more hydrophilic. Thesetreatments, which can include those employing self-assembled moleculesor a low-temperature plasma, are preferably performed on the initialthin coating of nipple body material on the fibers before the spacebetween them is filled. Alternatively, they can be performed on thefinished nipple after the fibers are removed. In addition, an additivecan be blended into the material forming the inner wall of thecapillaries. This hydrophilic additive will ultimately diffuse to thesurface of the inner wall of the capillaries and accumulate thereforming a hydrophilic layer.

A wide variety of hydrophilic materials are available and described inthe medical and patent literature. Examples of hydrophilic materialsinclude naturally occurring proteins such as soy extract (Pro-Coatavailable commercially from Protein Technologies Int., St. Louis Mo.)and polymers such as nylon 66, hydrophilic polyurethane (Hydrothane™available commercially from Cardiotech Int., Woburn Mass.) acrylate,polyacrylonitrile, or methacrylate. Also suitable for treating orcoating a hydrophobic polymer to make the surface hydrophilic aremetallic coatings, fluoro polymers commercially available from Dupont,Slip-Coat® available commercially from STS Inc., Henrietta N.Y., as wellas Chemstat® and Maxomer® both available commercially from ChemaxPerformance Products, Greenville S.C., hyaluronic acid, and surfactantssuch as the alkyl diethanolamides, including lauric diethanolamide andstearyl diethanolamide, glycerol esters and anionics. These materialsmay be applied by spraying, wiping, immersion, or other means, so longas appropriate measures are taken to provide a proper coating thickness,typically in the range from 0.025 μm to 1.0 mm, usually from 0.05 μm to1 μm.

In a separate, but ultimately equivalent sequence of processing steps,the fibers can be coated with hydrophilic material before the nipplebody material or nipple body material precursor is placed around thefibers. The requirements for this hydrophilic coating material are thatit be non-toxic, insoluble in water to the extent that it is notsignificantly affected by boiling water, and not adversely affected orremoved by the procedures used to place the nipple body material aroundthe coated fibers or to remove the fugitive fiber.

Inasmuch as the nipples of the present invention deliver fluid to thefeeding tip by capillary action, the nipples have the potential todeliver fluid at an undesired rate or when it is not desired. Forexample, if the baby bottle is tilted to the extent that fluid contactsthe fluid delivery passages at the flange (bottle) end of the nipple,the fluid will drip out of the passages at the end of the feeding tip.

There are several conventional solutions for this dilemma. It is ofcourse possible to stop the dripping, for example, by keeping the bottleupright or by placing a tight fitting cap-like device over the tip end24 of nipple 22 or the entire nipple when it is not in use.Alternatively, a much more acceptable solution is to make a very shortdistance from the capillary exit in the tip 24, on the interior wall ofthe capillary, hydrophobic. There are a number of ways in which this canbe done. If the material used to fabricate the nipple body ishydrophobic, then the hydrophilic coating or surface treatment on theinterior surface of the fluid-delivery passages can be employedeverywhere along the capillary walls except for a short distanceextending inward from the exterior end of tip 24. That is, for example,either the hydrophilic coating is not applied in this region or it isremoved from this region, for example by mechanical or chemical means.If the nipple body material is hydrophilic, then the feeding-tip 24 canbe treated by a process consisting of a mechanical process, chemicalprocess, low temperature plasma, or radiation in order to make a smallportion of the length of the fluid-delivery passages extending inwardfrom the exterior end of the baby feeding-tip hydrophobic.Alternatively, a hydrophobic layer can be applied to the capillary wallfor a short distance extending inward from the exterior end offeeding-tip 24. This short distance can range from about two capillarydiameters or thicknesses, up to about ⅛-inch.

A wide variety of hydrophobic coating materials are available anddescribed in the literature. Suitable coating materials includefluoropolymer coatings, such as Fluoropel, Fluorothane ME, FluorothaneMU, and Fluorothane M1 available commercially from the Cytonix Corp.,Beltsville MD, as well as those available from DuPont. In addition,almost all polymers known are hydrophobic and can be used as coatings.These materials may be applied by spraying, wiping, immersion, or othermeans, so long as appropriate measures are taken to provide a propercoating thickness, typically in the range from 0.025 μm to 0.5 mm,usually from 0.05 μm to 1 μm. these coatings must not be soluble inboiling water, non-toxic, and not affected by manufacturing proceduressubsequent to their application.

Regardless of how the hydrophobic region extending inward from theexterior end of the feeding tip is created, its presence providesanother function in addition to that of preventing unwanted dripping.That is, it allows the water-based fluid to go up the entire capillaryto the very end of the feeding tip and then stop. This brings the fluidvery close to the infant's mouth and eliminates hard sucking, but allowshim to control the amount that he receives in a given time by thestrength of his sucking. Thus, fluid will not be delivered too quicklyfor the infant to swallow it. Obviously, the amount of liquid that theinfant receives for a given sucking effort can also be accuratelycontrolled by the dimensions of the fluid-delivery pathways. This is notpossible with the prior art.

Since microscopic capillaries with variable axial geometry can beproduced using microtube technology, tapered fluid-delivery passages orcapillaries, such as seen in FIG. 3 can be produced. FIG. 3 shows a babynipple 34 with tapered fluid-delivery passages 36. The taper of passages36 is exaggerated for the purpose of illustration. Other referencenumerals in FIG. 3 are the same as in FIG. 2, since the elements are thesame. Fluid-delivery capillary passages of this shape will increase thefluid flow to the baby when compared to a capillary passage with aconstant diameter equal to the minimum diameter of the taperedcapillary. At the same time the tapered capillary will preferentiallydirect fluid flow towards the baby's mouth.

Nipples 22 (FIG. 2) and 34 (FIG. 3) are of single piece construction,with the nipple body made from a single elastomeric material. It is alsopossible to provide a nipple fabricated from at least two components,composed of the same or different materials. Referring to FIGS. 4 and 5,there is seen a nipple 38. Reference numerals 24, 26, 28 and 30 are thesame as in FIGS. 2 and 3 because the elements are the same. Nipple 38differs from the previously described nipples in that nipple 38comprises a separately fabricated capillary bundle core 40. The body ofcore 40, shown separately in FIG. 6, is solid and has at least one fluiddelivery passage 42. Each fluid-delivery passage 42 has a hydrophilicinterior surface, at least one cross-sectional dimension in the range of1-2000 microns and is aligned in such an orientation as to deliverwater-based fluid from the bottle or other container to a sucking infanton the other end by capillary action.

The nipple core 40 can be fabricated by numerous means such as molding,dipping, pultrusion or extrusion in which the capillary-forming fiber orfibers are held in the desired position for producing a core perform.Nipple core material 44, which can be the same as or different from theelastomeric material used to form the nipple body, is then placed aroundthe at least one fiber until the lateral dimensions of the nipple coreare achieved. If there is more than one fiber, nipple core material 44is used to completely fill the space between the fibers, and also tosurround the outer fibers forming a consolidated core preform.Alternatively, other means such as, coating the fibers using a liquid,vapor, or gaseous nipple body precursor material can be used followed byany necessary conversion to the nipple core material.

As mentioned above, the material 44 used to form the core 40 can be thesame or different from the elastomeric material used to form the nipplebody. For example, the nipple core material may be more firm or rigidthan the nipple body material in order to better keep the fluid-deliverycapillaries open when the baby bites on the nipple. In addition, itshould be noted that it is not necessary for the elastomeric nipple bodymaterial to be hydrophilic. That is, the nipple core material can behydrophilic while the elastomeric nipple body material is hydrophobic.Alternatively, if the nipple core material is also hydrophobic, thefugitive fiber can be coated or the inner surfaces of the capillariesformed after fugitive material removal can be treated or coated asdescribed above to make them hydrophilic.

Since the nipple core 40 does not have radial dimensions that equal orexceed the exterior nipple dimensions, additional material must be addedto form the finished nipple. Nipple core 40 is placed in a suitablemold. Sufficient nipple body material is then injected into the mold tofill the mold. After solidifying the nipple body material, byappropriate technique, the nipple is removed from the mold andsufficient solidified nipple body material is removed from the tip endand from the flange end to expose the end(s) of the fugitive fiber(s).The fugitive fiber(s) is(are) removed as described previously, therebyleaving fluid-delivery passages with interior dimensions equal to orless than the external dimensions of the fugitive material.

Alternatively, nipple body material can be placed around theconsolidated core preform producing a body larger than needed for thenipple. This might be done, for example, by pultrusion in a continuousor sequential process. Using this technique, the consolidated corepreform surrounded by the nipple body material would have to be both cutto length and perhaps have excess nipple body material removed to obtainthe final dimensions needed for the nipple.

In another approach, shown in FIG. 7, a consolidated core preform and anipple body 46 with net external dimensions and a hollow central portion48 positioned along the principle axis can be fabricated separately. Inthis case the interior dimensions and shape of the hollow centralportion 48 of the nipple are approximately equal to the exteriordimensions and shape of the consolidated core preform 40. The nipplebody with a hollow central portion would then be placed around theconsolidated core preform of appropriate length and friction-fitted,bonded and/or sealed to it with a leak-free interface. It should benoted that if the hollow central portion 48 in the nipple body isslightly smaller in dimension than those of the consolidated corepreform, it is possible to form a leak-free interface simply byfriction. However, if the dimensions are approximately equal or if thedimensions of the consolidated core preform are slightly smaller thanthose of the nipple hollow core in the nipple body, some sort of a sealwill be required to make a leak-free interface. Placing the consolidatedcore preform in the nipple body can be done in a number of ways such as,sliding the consolidated core preform into the hollow nipple body orsegmenting the hollow nipple and then rejoining the parts. If both theconsolidated core preform and the nipple body were tapered or if thehollow central portion in the elastomeric nipple body were slightlyunder-sized a leakfree interface could be formed without any heat,sealant or bonding material. Of course, the consolidated core preformcould be placed and then bonded or sealed in a piece of nipple bodymaterial larger than needed for the nipple. However, this requires anadditional step of removing excess nipple body material. Regardless ofhow the complete nipple is formed, in the final step, the fibers areremoved to produce the capillaries by a process appropriate for theparticular fiber such as reaction, solvation, phase change, or otherappropriate technique that does not adversely affect the flexible solidmaterial of the nipple or the material of the core. It should bementioned that in many cases it may be necessary to remove some nipplecore material from the ends of the fibers in order to remove them.

Finally, in all of these nipples made with a core it is important tomention that the length of the nipple core does not have to equal thelength of the nipple body. For fluid delivery it is necessary that thefluid delivery capillaries be the same length as the nipple core.However, it is not necessary that the length of the core equal that ofthe body. For example, the core can be placed only in the upper tipregion of the nipple, which still keeps the tip portion that is in theinfants mouth from closing off. In this design, the lower body of thenipple is hollow and thus part of the fluid reservoir. This design iscloser to the conventional nipple design and requires less material tomanufacture than a nipple with a core length that equals the length ofthe nipple.

If fugitive material is used to form the hydrophilic fluid capillariesin a nipple core, there is another means to fabricate hydrophiliccapillaries with a short hydrophobic region. In this method at least onepiece of fugitive material is placed and held vertically in a container.(Alternatively, the fugitive material can be placed in a centrifuge tubeand held parallel to the axis of the tube by centrifugal force.) Thiscontainer can either be a mold with the radial or transverse dimensionsof the nipple core or can be a larger container in which more than onecore can be formed simultaneously. If there is more than one piece offugitive material they can be aligned and held parallel to one anotherand placed vertically in a container. Hydrophilic material is thenplaced in the container to fill the space between the fibers to aheight, which is equal to or greater than the desired length of thehydrophilic region of the capillary. When the hydrophilic material hassolidified and cured, hydrophobic material is added to fill the spacebetween the fibers to a height that is equal to or greater than thelength of the desired hydrophobic region of the final capillary. Afterthe hydrophobic material is solidified and cured, individual nipplecores are removed from the molds or from the solidified slab and thenshaped by cutting, punching, or coring the solidified material parallelto the principal axis of the fugitive material. After the corecross-section is shaped, material can be removed from the ends ifnecessary to bring the length of the hydrophilic and hydrophobic regionsto the desired length. The final step in making the core is to thenremove the fugitive material. Of course, the process of filling thespace between the fibers can be performed in reverse starting with thehydrophobic material. In addition, if the hydrophobic and hydrophiliccore material are not miscible, there is no need to cure the firstmaterial before the second is added.

An alternate technique to produce a hydrophobic region at the tip of thenipple, is to incorporate a very short space between the core and theexternal tip. This space acts as a reservoir between the hydrophiliccapillaries in the core and microscopic hydrophobic passages in the formof capillaries, pores, or holes in the tip. These hydrophobic passagesin the tip can be in the form of microscopic holes formed in a thinsection of nipple body material in the tip or in the form of a thinhydrophobic membrane inserted in the tip. The combination of capillariesand reservoir work together to bring liquid to the tip while thehydrophobic passages in the tip prevent liquid from exiting the nippleunless there is a slight pressure differential.

The cross-sectional shape of the capillaries in this application can beany desired shape. For example, the fibers used to create thecapillaries can have the shape of a “C”, an “X”, a “Y”, a “V”, or thelike. For baby bottle nipples some of the preferred shapes for thecross-section of the capillary include trilobal 50, as shown in FIG. 8,as well as rectangular 52 with a high-aspect cross-sectional ratio(width:height), as shown in FIG. 9. These cross-sectional shapes havethe feature of being difficult to clog with particulates. With therectangular cross-section, if the capillary walls are rigid, the smallerdimension can be made as small as practical to increase capillarypressure on a wetting fluid while the larger dimension can be increasedto allow maximum throughput of liquid. Obviously, nipples can befabricated with rectangular cross-sectioned capillaries using materialswith rectangular cross-section and procedures as described previously.

In yet another approach, a core preform with rectangular cross-sectionedcapillaries can be fabricated using a stacking layer approach that makesuse of fugitive layers rather than fugitive fibers. Referring to FIG.10, layers of fugitive material 54 are laid up in alternate layers withcapillary separation material 56, i.e., the material that separates thecapillaries which can be the same as or different from the nipple bodymaterial, to a desired thickness, e.g., about 1-6 mm. The resultingassembly is then consolidated into one piece using heat, pressure,solvent, or the like. Following consolidation, individual nipple corescan be machined or cut from this one piece, for example, by cuttingalong the cut lines 58, thus providing a nipple core 60, as shown inFIG. 11.

Alternatively, this build-up of alternate layers of fugitive andcapillary separation material can be accomplished using techniques suchas, extrusion of individual or multiple layers, pultruding one layermaterial while filling in with the other, spraying layers, castinglayers, lay-up of films, and the like. These processes can be continuousor the layered structures can be formed in a batch process. The productof this layering process can be large pieces of layered material fromwhich individual layered structures are cut or machined, or layeredstructures or complete nipples can be fabricated individually, forexample in a mold. By using layers of varying thicknesses and widths,the shape of the capillaries can be controlled. Thus, it is possiblewith this technique to produce tapered capillaries.

Using the lay-up technique, the constrained layers can be formed into afree-standing layered structure in which the alternating layers ofcapillary separation material and fugitive material are formed into onepiece using heat, evaporation, pressure, solvent, pultrusion, adhesives,curing, mechanical interlocking, etc. It should be noted that thetechnique employed to produce a layered structure must produce acapillary separation layer with a hydrophilic surface after the fugitivematerial is removed. To aid in removal of the fugitive material it ispossible to leave minute gaps (on the order of microns or tens ofmicrons) between portions of the fugitive and separation layers duringfabrication. This will increase the rate of fugitive material removalwithout appreciably decreasing the capillary pressure and thus thedelivery of the fluid to the infant.

Since the nipple core 60 does not have radial dimensions that equal orexceed the exterior nipple dimensions, additional material must be addedto form the finished nipple. This can be accomplished, for example, bycutting the consolidated core preform to length and placing it in ahollow nipple body as described above or by placing it in a mold havingthe final shape of the nipple. The mold is then filled with elastomericnipple body material or a nipple body precursor material and solidifiedproducing a net-shaped nipple. The fugitive layers are then removed, aspreviously described for fugitive fibers. The resulting nipple is shownfrom the flange end in FIG. 12. Obviously, it is necessary to have onlyone capillary formed by the removal of one layer of fugitive material inorder to transport fluid through the nipple. However, with more layers,they can be made thinner which increases capillary pressure and thusfluid delivery through each capillary formed by the removal of thethinner layers of fugitive material. An additional result is thatthinner capillaries will decrease the amount of sucking effort on thepart of the infant to obtain fluid through the nipple. In general, thefugitive layers should have a minimum thickness of about 20 microns withan aspect ratio (width to thickness) of about 100:1 to 10:1.

The preferred fugitive materials are non-toxic and water-soluble andinclude polyvinyl alcohol and natural water-soluble materials. Theremoval of the fugitive layers is enhanced if the layers of fugitivematerial are hollow or porous.

The surfaces of the capillary separation layers form the major walls ofthe capillaries after the fugitive material is removed. Nipple bodymaterial, nipple core material, another material such as a naturalprotein or a combination of materials can be used directly as acapillary separation layers if the surfaces of these capillaryseparation layers are hydrophilic. A combination of materials in thecapillary separation layer can be used, for example, to modify andtailor the rigidity of the layered structure. If the individualcapillary separation layers do not have a hydrophilic surface they canbe surface-treated or coated with a hydrophilic material to make themeither hydrophilic or more hydrophilic.

If the capillary slit formed by removal of the fugitive material has asignificant width or length, it is possible for an infant to close thecapillary by biting, if the material used to form the layered structurehas sufficient flexibility. To allow the use of flexible materials orthin brittle materials, it is possible to incorporate supports that willhelp keep the capillaries open. These supports, which can be seen inFIG. 13, not only provide mechanical support but also decrease thelateral size of the individual capillaries. Numerous methods can be usedto form these supports.

FIG. 13 shows a layered structure comprising a plurality of layers ofplain, i.e., flat, sheet or film 62 alternating with a plurality oflayers of shaped sheet or film 64. Referring to FIG. 14, it can be seenthat the shaped layer 64 has projections or supports 66 on both sides.When layer 64 is stacked with layers 62, as seen in FIG. 13, withprojections 66 aligned in the axial direction, the supports thus definea plurality of capillaries 68. Shaped layer 64 can be formed by molding,rolling, casting, extrusion, pultrusion or embossing. Obviously, thedegree of layer separation and thus the capillary thickness can becontrolled by the height of the supports 66, the depth of thedepressions, or both. If desired, the recesses defined by supports 66,in FIG. 14, can be filled with a fugitive material to maintainstructural integrity while the layered structure is being fabricated. Avariant stacked structure is shown in FIG. 15, wherein a plurality ofshaped layers 70 with projections 72 on one side are assembled with asingle layer of plain sheet or film 74. Individual nipple cores can bemachined or cut from this layered structure as described previously.

It should be noted that in layered structures of the type shown in FIGS.13 and 15 that there are two differences from the previous layeredstructures. The first is that both surfaces of the shaped layers must behydrophilic. The second difference is that if the individual layers arenot well bonded to or held by the nipple body material, it is possiblefor the layers to shift with respect to one another. Depending on thenumber of slit-shaped capillaries this might significantly affect flowby eliminating some of the capillaries. To solve this problem the layerscan be joined to one another using techniques, such as, gluing, bondingand mechanical interlocking.

Mechanical interlocking to keep layers from shifting with respect to oneanother during manufacture or use can be accomplished in a number ofways. An example of mechanical interlocking of three layers 154 is shownin FIG. 25. Each layer 154 has a top face 156 and a bottom face 158.Each top face 156 has two depressions 160 and each bottom face 158 hastwo projections 162. Each top face 156 can also have an optionalprojections 164. Each depression 160 has a depth 166 and eachprojections has a height 168. Projection height 168 is greater thandepression depth 166, so that when the layers 154 are fitted together,rectangular capillaries 170 are defined between layers. The projection164 serves as a support in the center of each capillary 170 to keep thecapillary open under applied pressure. The thickness of capillaries 170and the height of projection 164 is equal to height 168 less depth 166.Those skilled in the art will recognize that more than one projection164 can be used. In general, the height of projections 162 is about 40to 1000 microns with a spacing between projections of about 100 to 1,500microns, and the depth of depressions 160 is about 20 to 1000 micronswith a spacing between depressions identical to said spacing betweenprojections, and the difference between projection height and depressiondepth is at least 30 microns.

Capillary layers can also be formed as concentric or near-concentricrings, as shown in FIG. 16. In this example, nipple core 76 has a solidcore 78 with three concentric capillary-defining rings 80, 82 and 84.Each of the rings 80, 82 and 84 has a plurality of spaced apart,inwardly directed spacers 86 which define capillaries 88. Core 76 can befabricated by co-extruding a suitable elastomeric core material with asuitable fugitive material filling the areas which, after removal of thelatter, define the capillaries 88, through an appropriately shaped die.Alternatively, a similar core with a jellyroll structure can befabricated by winding a shaped layer, such as item 70 in FIG. 15, arounda solid core.

Another approach for making microscopic pathways in the nipple involvesusing hollow fibers. These can be spun individually and placed in asolid nipple or a single multi-hole hollow fiber can be extruded,directly producing a core with capillaries. Except for fiber removal,the processing of these hollow fibers into finished nipples is verysimilar to that already described for microtube technology starting withsolid fibers. The use of hollow fibers is one of the preferred methodsof fabrication if the material used to form the hollow fiber or hollowfiber bundle is a material of choice for the capillary wall. That is,with hollow fibers the step of fiber removal is eliminated. Thus, if theinner wall of the hollow fiber does not have to be coated, a multi-holehollow fiber core can be easily extruded, cut to length and inserted ina prefabricated nipple body as described previously. Alternatively, theinterior of the capillaries could be coated if necessary and theextruded and cut-to-length hollow fiber core could then be inserted intoa mold and the material used to form the nipple body placed around it,if the material used to form the body does not wet the hollow fiber. Theuse of hollow fibers greatly decreases production time. Of course, thisalso applies to other forms of hollow tubing. In particular metallictubing, such as 316L stainless tubing, which is robust, hydrophilic, andalready used in food processing, can be employed.

A further approach is shown in FIG. 17, which illustrates a nipple 90having a reticulated porous core 92. Nipple 90 has a rounded tip 94 atits top end. Tip 94, which is shown as rounded, but can be flat or haveany shape. Below the rounded tip 94, the nipple 90 flares outward toform a torso 96. Below torso 96, the nipple flares outwardly, asindicated at 98, for mounting to a bottle with a compression fitting,not shown. Since the nipples of the present application are not hollowrubber shells, there is no need for an outwardly extending flange tomount them to the fluid container, as previously shown. The shape of thenipple and the means of attachment of the nipple to a fluid containerare not central to this application.

The reticulated porous core 92 can be a foam, a sintered polymer or asintered metal, so long as it provides an interconnected pore network inplace of the capillaries produced by the previously described methods.This interconnected pore network is formed from the interconnected cellsor voids in the porous materials. For fluid delivery, the reticulatedporous material needs to be non-toxic and hydrophilic or the surface ofthe pore network needs to be coated with a nontoxic, water-insolublehydrophilic coating. An example of a hydrophilic foam is thepolyurethane foam described by Wood, U.S. Pat. Nos. 3,903,232 and4,137,200, while an example of a sintered metal is stainless steel, andthat of a hydrophilic sintered polymer is polyurethane. Of course, ahydrophobic foam or porous sintered material coated with a hydrophilicmaterial could also be employed for fluid delivery.

Since only a portion of the nipple, usually the central axial portion ofthe nipple, and not the whole nipple should allow milk or water-basedfluid to pass through, it is not possible to have a nipple made entirelyof a reticulated porous material. Thus, in nipples using a porousmaterial as the microscopic pathways for capillary action, the nipple 90would consist of a porous core 92 surrounded by the nipple body made ofelastic material, which must not permit the flow of liquid.

To manufacture a porous core nipple 90, the porous core 92, has to beformed into the proper shape. This would involve the use of one or moretechniques, such as, molding, machining, or extrusion. The porous corecould be made net-shape or its dimensions could be decreased to finaldimensions. Once the porous core is in the proper shape for the nipple,the flexible nipple body, which must not be able to pass fluid, isformed or placed around the porous core 92. The flexible material forthe nipple body can be formed or placed around the core in a number ofways. For example, the flexible nipple body material can be molded intothe proper external shape and then machined if necessary so that thereis a hollow central region to accept the porous core. Alternatively, thenipple could be formed to net shape with a hollow core. The porous coreis then placed in the nipple body and sealed and/or bonded to the nipplebody by friction, heat, an adhesive, or sealant that does not wet theporous material. Alternatively, the porous core can be placed in asuitable mold, after which a suitable nipple body material is injected,then cured or otherwise solidified to provide a nipple.

One additional method of making a porous-core nipple using reticulatedfoam is to form the porous core within a previously fabricated nipplebody 90. That is, the nipple body is formed to net shape or near-netshape with a hollow central portion down the axis in the middle of thenipple. The surface of the hollow central portion in the nipple body canbe made tapered or irregular for mechanical interlocking. The non-toxichydrophilic foamed core is then formed completely filling the core inthe nipple body using appropriate foam-forming techniques. The foam isthen trimmed if necessary.

Regardless of how the foam core is formed, if the foam is not rigid,there is the possibility that it can be collapsed by an infant biting onthe tip of the nipple. To prevent this, a thin rigid structural support93 can be placed around the foamed core 92 in the nipple tip 94 alongthe entire length of the foam core. This thin rigid structural supportcan be placed around the foam before it is inserted into the nipple bodyor can be placed in the hollow core channel in the nipple body beforethe foam core is inserted or formed there. Alternatively, the nipplebody can be formed around the structural support 93, and the foam corethereafter inserted or formed therein.

In order to prevent clogging of the relatively long fluid-deliverycapillaries in the baby bottle nipple, it is possible to usefluid-delivery capillaries of desired cross-sectional shape or variableaxial shape. In addition, for nipples utilizing either capillaries orreticulated porous material for fluid delivery, it is also possible toplace a pre-filter between the container's contents and the nipple. Thistype of pre-filter is especially necessary for the nipple with taperedfluid-delivery capillaries such as seen in FIG. 3. Without thepre-filter, the tapered fluid-delivery capillaries can be clogged by anyparticles that enter the end of the capillary with the largercross-sectional area, and are larger than the minimum capillarydimension. As noted previously, the minimum cross-sectional dimension ofthe pores or capillaries in the filter must be smaller than those thatdeliver milk or other water-based fluid to the infant so that they caneffectively keep particulates that would clog the fluid-delivery poresor capillaries from entering the nipple. It is preferred that theminimum cross-sectional dimension of the pores or capillaries in thefilter be significantly smaller that those that deliver milk or otherwater-based fluid to the infant, i.e., about 25% to 75% smaller than thefluid delivery pores or capillaries.

FIG. 18 illustrates a nipple 100 with an integral filter 102. Nipple100, like nipple 90 shown in FIG. 17, has a rounded tip 104 at its topend. Tip 104, which is shown as rounded, but can be flat or have anyshape. Below the rounded tip 104, the nipple 100 flares outward to forma torso 106. Below torso 106, the nipple flares outwardly, as indicatedat 108, for mounting to a closed container 109 with a compressionfitting. Nipple 100 is shown as having a separately fabricated capillarybundle core 110, as discussed previously with regard to FIG. 4, althoughthe invention is not limited thereto. Filter 102 comprises a pluralityof bundles of capillaries or pores 116, such as those seen in FIG. 23.

Below the flare 108, nipple 100 extends downwardly to form a skirt 112,which includes an inwardly directed shoulder 114 for holding filter 102apart from the fluid delivery passage 110, thereby providing a reservoir118. Reservoir 118 is necessary because the position of the pores orcapillaries in the filter and the nipple may not match. If the ends donot properly align, the pores or capillaries in the filter will not beable to feed the fluid-delivery capillaries in the nipple. The nipple100 and filter 102 can be mounted to a bottle 109 using a compressionfitting (not shown), as discussed previously. FIG. 18 also exhibits avent plug 105 containing the air-admittance capillaries 107 in thebottom of the container. In this figure, the plug and capillaries havebeen enlarged for clarity.

In contrast to the integral filter 102, the filter can also beunattached, as shown in FIG. 19, which illustrates a nipple 118 and afilter 120. The nipple 118 and filter 120 can be mounted to a closedcontainer 109 using a compression fitting (not shown), as discussedpreviously. One requirement for this separate, unattached filter is thatthe filter or the nipple provide a small clearance or reservoir, as at122, between the filter and the fluid delivery pores or capillaries ofthe nipple.

Nipple 118, like nipple 90 shown in FIG. 17, has a rounded tip 124 atits top end. Tip 124, which is shown as rounded, but can be flat or haveany shape. Below the rounded tip 124, the nipple 118 flares outward toform a torso 126. Below torso 126, the nipple flares outwardly, asindicated at 128, for mounting to a bottle with a compression fitting,not shown. Nipple 118 is shown as having a reticulated porous core 130,as discussed previously with regard to FIG. 17, although the inventionis not limited thereto. Filter 120 comprises an optional structural ring132 filled with a reticulated porous material 134.

FIG. 19 also shows a vent plug 105 containing the air-admittancecapillaries 107 in the side of the container. In this figure, the plugand capillaries have been enlarged for clarity.

As stated previously, one of the major problems with current babyfeeding systems is that a vacuum can be formed in the fluid container asa result of the infant's sucking. As the baby sucks harder to overcomethe vacuum, he/she can swallow air, sometimes with very negativeresults. To alleviate this problem it is necessary that the pressureinside the bottle be continually equalized with the external pressure byadmitting air into the baby bottle delivery system at a rate that issubstantially equal to the rate at which the liquid is being withdrawn.This present application addresses this problem in a very unique manner,by employing hydrophobic microscopic pores or capillaries either in thenipple or elsewhere in the fluid delivery system such as the containeror the mounting hardware to admit air. Only hydrophobic pores orair-admittance capillaries in the nipple will be discussed herein,although it should be noted that a portion of or all of the fluidcontainer or mounting hardware can contain or be made of a materialpossessing hydrophobic pores or capillaries. It should be noted that theuse of these air-admittance components is not limited to nipples withfluid-delivery capillaries; they can become components of any nipple orbaby bottle delivery system currently on the market. Theseair-admittance components can also be incorporated into any part of aclosed container normally used for dispensing a water-based fluid, suchas toddler drinking cups, sports drinking bottles, and the like. FIG. 18shows a vent plug 105 containing the air-admittance capillaries 107 inthe bottom of the container, while in FIG. 19 the vent plug 105containing the air-admittance capillaries 107 is in the side of thecontainer. In both these figures, the plug and capillaries have beenenlarged for clarity. Because the walls of these pores or capillariesare not wet by water, i.e., water forms a contact angle of greater than90 degrees with the surface, these pores or capillaries will allowentrance of air into the fluid container to counteract the vacuum butwill not allow the egress of fluid, if the pores or capillaries areproperly sized and positioned. This will solve two problems associatedwith the prior art. Not only will weeping through the vent holes beavoided, but there will not be a problem of cleaning and sterilizingthese air-admittance pores or capillaries since fluid will not enterthem. These hydrophobic air-admittance capillaries or pores can belocated anywhere in the nipple that is not in the infants mouth whilesucking. The hydrophobic air-admittance component(s) can take anyexternal shape, such as, a plug, core or disc and can be fabricated bythe same techniques employed for the fluid-delivery passages. Theair-admittance passages can also take the form of microscopic holes orpores that pass through a nipple body made of a hydrophobic material.Alternatively, any hydrophobic microporous reticulated material can beinserted and sealed in the nipple body.

It should be noted that there are some differences between an airadmittance device utilizing capillaries and a device utilizingmicroporous material as the pressure equalizing pathway. Thesedifferences point out the superiority of utilizing capillaries over amicroporous material for air admittance.

A microporous material cannot guarantee an exact pore size, but ratherprovides a distribution of pore sizes around some average value. Thisdistribution of pore sizes does not allow for a precise thresholdpressure for liquid breakthrough on the basis of a precise poredimension as is the case with capillaries of precisely controlleduniform cross-sectional dimension. Also, the straight concave walls ofan essentially 2-dimensional capillary entrance offer much greaterresistance to liquid entrance than the 3-dimensional convex curvedligands or particle surfaces present in a microporous material.

Although a capillary air admittance device is superior to a microporousair admittance device, there are also differences in effectiveness amongmicroporous devices. The effectiveness of a microporous air admittancedevice depends on the percentage of the pores that are open and gothrough the entire device. That is, the size and number of pores perunit volume is not relevant if the pores are closed or do not connectwith a network that goes through the device. Thus, it is important thatthe microporous material be highly reticulated. With a high qualityreticulated material, an air admittance device can be made with a verysmall cross-sectional area (<0.5 cm² and preferably less than 0.2 cm²)and still be very effective in eliminating a partial vacuum in a closedcontainer. The use of a highly reticulated material greatly decreasesthe amount of material needed and the size of the device whichsignificantly decreases the cost.

FIG. 20 illustrates a nipple 136, otherwise configured as disclosedpreviously, also comprising at least one hydrophobic air-admittancemeans or device 138. These air-admittance means 138 can beair-admittance capillaries or air-admittance reticulated porousmaterial, and are similar in configuration to the fluid-deliverypassages disclosed hereinbefore, with the exception that they arehydrophobic. The air-admittance capillaries or reticulated porousmaterials can be in multiple locations throughout the nipple, such as at180-degrees apart, two such air-admittance means being shown in thisfigure. An example of a hydrophobic foam is the polyurethane foamdescribed by Kehr et al, U.S. Pat. No. 3,959,191.

Nipple 136 can be fabricated in a manner similar to fabrication of thenipple shown in FIG. 4. That is, a separately fabricated fluid-deliverycapillary bundle core and a separately fabricated air-admittancecapillary bundle core are placed in a mold having the final shape of thenipple. The mold is then filled with elastomeric nipple body material ora nipple body precursor material and solidified producing a net-shapednipple. The fugitive material is then removed, as previously described.

Alternatively, nipple 136 can be fabricated by other means. For example,the fluid-delivery capillary bundle core, the air-admittancecomponent(s), and the nipple body can all be fabricated separately. Inthis case the molded nipple body contains a void for the capillarybundle core, such as the hollow central portion 48 in FIG. 7, and one ormore shaped voids for the pre-fabricated air-admittance component(s),which can be in the form of an air-admittance capillary bundle core, aporous reticulated core, or a thin porous membrane. The fluid-deliverycapillary bundle core and the air-admittance component(s) can be held inplace by the various methods previously described. Although theair-admittance devices are, in this embodiment, incorporated into thenipple of a baby feeding bottle, such devices can be positioned anywherein the container or lid. Such device can be fabricated as an integralpart of the container, such as capillaries formed directly in thecontainer wall or molding the container around the device.

Alternatively, the device can be permanently placed in a pre-formed voidin the container or lid after manufacture by, for example, the use of anadhesive, grommet, or foaming technique. Additionally, the device can beattached to the container or lid with a temporary means, such as with ascrew thread or snap so that it can be removed to enhance cleaning ofthe container.

It is within the scope of this invention to provide a nipple wherein thenipple body that is not in the child's mouth can function as a path forair-admittance. Referring again to FIG. 4, a separately fabricatednipple core 40 is placed in a suitable mold. Sufficient body materialwhich will form a hydrophobic reticulated foam is then injected into themold to fill the mold. After solidifying the nipple body material, byappropriate technique, the nipple is removed from the mold andsufficient solidified nipple body material is removed from the tip endand from the flange end to expose the end(s) of the fugitive fiber(s).The fugitive fiber(s) is(are) removed as described previously, therebyleaving fluid-delivery passages with interior dimensions equal to orless than the external dimensions of the fugitive material. Since thereticulated foam body material has no mechanical strength, it offerslittle resistance to the biting of an infant. Therefore, either the corematerial must be rigid or it must be surrounded on its exterior with arigid material.

The minimum dimension of the hydrophobic pores or capillaries forair-admittance will depend on the hydrophobic material that is on theinterior pore or capillary wall and the contact angle that thewater-based fluid makes with it. In general, the minimum cross-sectionaldimension of the air-admittance pore or capillary will be such that adifferential pressure of at least 1 psia will be required to force thewater-based fluid through it. These air-admittance hydrophobic pores,i.e., reticulated porous material, or capillaries, should have across-sectional dimension of about 0.1 to 200 microns, preferably about1 to 50 microns. It is presently preferred that such capillaries have aconstant axial diameter. In contrast to prior art nipples, in whichthere is a vent hole in the nipple, the air-admittance pathways of thepresent invention do not leak because they are smaller. That is, insteadof using a large hole for air-admittance that will leak because it issized for an adequate rate of air-admittance to equalize the vacuumcaused by liquid removal, the capillaries or pores of the presentinvention are much smaller and more numerous to allow for an adequaterate of air-admittance while at the same time preventing liquid egressbecause of the smaller diameter and the hydrophobic inner surface. Incontrast to the fluid-delivery capillaries, which must have asignificant length to traverse the solid axial portion of the nipple,the air-admittance pores or capillaries can be in the form of a thinmembrane if the contact angle is high enough and the pore size is smallenough to prevent the ingress of fluid.

In all of the nipples made with a separately formed core, the length ofthe nipple core does not have to equal the length of the nipple body.For fluid delivery it is necessary that the fluid delivery capillariesbe the same length as the nipple core. However, it is not necessary thatthe length of the core equal that of the body. Three examples are shownin FIGS. 21, 22 and 26 in which the core is shorter than the nipple.FIG. 21 illustrates a nipple 140 fabricated by inserting a short pieceof capillary bundle core 40 (see FIG. 6) into a nipple body 46 having ahollow central portion 48 (see FIG. 7). The resulting construction keepsthe tip that is in the infants mouth from closing off. In this design,the lower portion of the nipple is hollow and thus part of the fluidreservoir. This design is closer to the conventional nipple design andrequires less material to manufacture than a nipple with a core lengththat equals the length of the nipple.

FIG. 22 illustrates a nipple 142 also fabricated by inserting a shortpiece of capillary bundle core 40 (see FIG. 6) into a nipple body 46having a hollow central portion 48 (see FIG. 7). Nipple 142 has a shortopen space between the core 40 and the external tip 144. This space actsas a reservoir between the hydrophilic capillaries in core 40 andmicroscopic hydrophobic passages in the form of capillaries, pores, orholes in the tip 144. These hydrophobic passages in tip can be in theform of microscopic holes formed in a thin section of nipple bodymaterial in the tip or in the form of a thin hydrophobic membraneinserted in the tip. Such membrane can be supported mechanically using arigid support structure such as a ring. The combination of the reservoirand the hydrophillic passages in the core work together to bring liquidto the tip while the hydrophobic passages in the tip prevent liquid fromexiting the nipple unless there is a slight pressure differential.

FIG. 26 illustrates a nipple 172 that is similar to nipple 140 in FIG.21 with the exception that the lower portion of the hollow centralregion of the nipple body has been enlarged to produce a hollow bulbousportion 174 of the nipple body similar to that of a conventional nippleseen in FIG. 1. This hollow bulbous portion of the nipple body is nowpart of the fluid reservoir. This design is even closer to theconventional nipple design and requires even less material tomanufacture than the nipple 140 in FIG. 21. In contrast to the previousnipple designs in which the solid portion of the nipple extends thelength of the nipple, in this nipple, the solid portion of the nipplebody only extends the length of the shortened nipple core 178.

The thinner nipple body wall 176 in the lower portion of nipple 172 moreeasily allows the insertion of a self-supporting hydrophobic membrane ordevice 180 for air-admittance. This figure shows the membrane 180 heldin the nipple wall 176 between two flaps 182. The membrane can be moldedinto the nipple body or it can be placed in the nipple body after thebody has been manufactured. If it is placed in the body aftermanufacture, it can be placed (with or without a mechanical supportring) between flaps in the nipple wall as shown, or a mechanical supportring for the membrane in the form of a grommet, for example, can anchorthe membrane to the wall of the nipple body. A seal (if required)between the membrane and the nipple body can be any of those describedabove.

The hydrophobic air-admittance capillaries can be fabricated by any ofthe methods described for the hydrophilic fluid delivery capillarieswith the exception of the materials or surface treatments used. Inaddition to these methods described, the hydrophobic air-admittancecapillaries can also be fabricated by classical extrusion techniquesemploying gas-injection or the co-extrusion of a sacrificial material.In the same way the hydrophobic reticulated air-admittance membranes ordevices can be fabricated by the same methods used for the hydrophilicfluid delivery porous materials. They can also be fabricated utilizingmicroporous templates as well as sacrificial particles in connectionwith both foaming and sintering techniques.

Having thus described exemplary embodiments of the present invention, itshould be noted by those skilled in the art that the disclosures hereinare exemplary only and that alternatives, adaptations and modificationsmay be made within the scope of the present invention.

1. A food or beverage container having a water-based fluid, a partialvacuum and a plurality of air-admittance capillaries, wherein eachair-admittance capillary has a hydrophobic interior surface and at leastone cross-sectional dimension in the range of 0.1 to 80 microns, whereinsaid air-admittance capillaries admit air into the container whilepreventing passage of a water-based fluid therethrough.
 2. The containerof claim 1 wherein said air-admittance capillary has a constant axialdiameter.
 3. The container of claim 1 wherein said air-admittancecapillary is rectangular.
 4. The container of claim 1 wherein saidair-admittance capillary has a cross-sectional dimension in the range of1 to 50 microns.